The following is best described as how I think I know it. I advise to verify it with qualified electricians before accepting as gospel. I welcome any changes or clarifications to my thoughts.

Your amperage is not necessarily a static (fixed) number.

Watts = volts X amps

Say your microwave uses 1200 watts and you are on a campground supply that provides 120 volts. Using the above formula:

1200 watts = 120 volts X 10 amps

Now, let's assume that the campground you are at, isn't providing 120 volts to your camper, but only 110 volts. Using the same formula:

1200 watts = 110 volts X 10.909 amps

So your amps increased because your voltage decreased, as the appliance tries to use 1200 watts. A lot of camp grounds have voltage decreases (fluctuations) due to other campers using Air Conditioners, etc. They also can have power surges as well as the dips. You see a lot of this depending on how old the wiring is, the number of campers placing demands on the electrical system, and many more reasons.

I have a voltage monitor in my RV, and I observe some pretty good voltage swings at one campground I frequent. Lou has an even better monitor, as shown in his pic above.

Here is a calculator link so you can play with the different voltages to see the amps needed:

Watts - volts - amps - ohms conversion calculator
You stated that you have been able to use both your microwave and A/C at the same time before. Depending on what else you may have on at the time, when using both of these appliances, you are usually near the max load of 30 amps. If you factor in possible lower voltage at the campground, you now may be using higher amps, thus putting you over 30 amps.....thus your breakers doing what they are designed to do.

Your surge guard may have over voltage and under voltage thresholds at which it shuts power down. I think I have read some where this under number is around 103 volts....but don't quote me on that. However using that same number you would be pulling 11.65 amps

1200 watts = 103 volts X 11.65 amps

Before I went to a lot of trouble replacing RV breakers (it can't hurt anything though), I would see how much voltage fluctuation there is at the campground you are staying at...............which in turn changes the amps.......or I believe so. Your problem may be the campground voltage, and not your RV.

EDIT: More reading:

Learning to Live with 30 Amps
Power Protection