bigman,
As Hilt pointed out and I tried to ellude to earlier. It is impractical to turn a home into an 'impregnible fortress" but there are things you can do to make your house less attractive to thieves and prepare for a possible SHTF.
The primary goal is to make the house more time-consuming, noisy and difficult to enter without drawing unnecessary attention to the house.
Making a house less attractive to thieves:
Outside of a SHTF enviornment, it can be highly desirable to make your house less attractive to thieves. This is a risk/reward trade off to the thief, so you want to increase the risk while maintaining or decreasing the reward.
1) Make entry difficult and time consuming.
That's where fences and bushes come in. They make it more difficult to access the property and the entryways to the house. They're not going to prevent a determend thief from reaching your house, but might convince them to hit the neighbors house instead.
Other improvements here include reinforcing the lock areas of doors and door jams, adding dead-bolts. If you have wooden sashed windows, drill 2 1/8" hole through the corner of the window where the sashes over-lap when the window is closed (one each, right and left side) and insert a common nail into the hole through the inner sash and into the outer sash. This makes the window a lot more difficult to open. A dowel in the track of a sliding glass door or blocking the sash of a window that slides up to open.
You can also look into protective / security films for the windows and glass doors. 3M makes a nice line of polymer films that will dramatically slow someone trying to enter the house down.
2) Add securty monitoring or warning alarms. This could be a service like ADT or Brinks, or door, window, motion detectors that produce a siren when triggered. If someone is breaking in, you want to make sure they'll get your attention for a proper response.
3) Reduce causual observe awareness
Most thieves have observed a target before they break-in and steal things. Being able to see into a house clearly identifies the potential reward for the theft. You want to minimize the ability of someone to identify valuable items from outside the house. Close blindes and move expensive items away from the view of first floor windows.
Also, maintain an occupied "look" to the house with a few lights on, even when you're away from home. Most thieves would rather avoid an occupied house.
4) Keep the area lit.
A well lit exterior is a sizeable deterant to a thief. Most thieves don't want to be seen stealing, and normally forcing a thief to enter a well lit area to get in significantly increases the risk of being caught.
Something change when you're in a SHTF enviornment.
1) In a SHTF enviornment, the Risk/Reward curve has changed, the lack of services reduces the "risk" while meeting basic needs (like food and water) can be significant rewards. As a result, you may need to take additional steps, and the longer other people are without food and water, the more desperate and determined they will become.
2) Physical securty that significantly increases the time it takes to force entry is even more important. Secure and block first floor entry points other than your primary and possibly 1 alternate entry point. I like 2' x 4' sheets of 3/4" plywood, but others like 2x3 and 2x4s for this. The goal is to force a person to break / breech the board or sheet before gaining entry. I prefer to mount to the interior side past curtains so that the window looks the same from the outside. If your neighbors are boarding up from the out-side, exterior boarding will draw less attention.
In general, you want to try to prevent people from knowing that you have comfortable stores. Curtains, blinds, shades, etc that prevent light from inside the house from escaping and telling "have-nots" that you have power, food, and other basic needs.
Adding Ubrackets to the walls and 2x4 or 2x6 boards to bar the door can also be very useful to prevent entry through a door.
Short of specialized balistic materials, most house building materials are soft cover, they will not stop a bullet. Ceramic tiles will generally shatter and stop a handgun round, but even they generally don't stop rifle rounds. You can always consider adding some tiled walls if you think you might need hard cover in a gunfight at your house.
There are a number of other things you can do to improve the security but the general rules are:
Minimize changes what will draw attention to the house from the outside casual observer
Extend the time AND effort required to break-in
Minimize an outside observers ability to determine the occupancy and contents of the house.