The idea that the founding fathers disdained a standing army is romantic, but it isn't entirely true. Some of the founders, of course, truly did not want one. But, others thought they might be necessary, and accepted them because they believed the citizens would retain military arms to be able to defend themselves against the army should it become corrupt.
The world is now a very different place than it was when the founders debated and ratified the Constitution. Previous posters have correctly pointed out that isolationism has proven historically fallacious; it didn't prevent the rise of Nazism and if we'd sat out WW2, God knows the results. Nazism might still have been defeated, but what about a WW2 victorious Soviet Union? Who would have won the Cold War -- or, would there even have been one?
I agree with the militia concept, but we need to face it; they can't do it by themselves. Before the Revolutionary War, militias often accompanied the Redcoats in fighting of Indian attacks. The Redcoats were tolerant of them; but when the "SHTF" it was usually the militia guys who suddenly recalled they had forgotten to buy their wifey a birthday present, or had forgotten an appointment for a root canal, and ran away. Of course, once the Revolutionary War started, these guys had to actually learn to fight -- there'd be no one to shoot the Redcoats if they ran this time! In some cases, they did OKAY; along New York's Hudson River repeated militia attacks did do very well against the Redcoats ... but a lot of other places, they were undependable at best.
Remember, though, even Washington's Continental Army got their collective butts kicked out of NYC and the Hudson, and didn't achieve a victory until Trenton.
Machiavelli also was a proponent of a militia system. In his concept a few top officers and men would be constant members, train year round, and maintain and keep equipment. These people would always maintain the knowledge and experience of the warrior. During time of war the militia would be expanded to full size by enlisting the townsmen of the principality. These would be farmers and other civilians who would have some knowledge of things military and some experience with weapons.
Keeping an army trained up today takes a lot, with all the sophisticated weapons we have. At certain times in our history we have given this short shrift. But overall we've done mediocre to pretty good in recent decades.
Should we trust the military? Yes, absolutly we should and we should support them. In some ways I think you have conflated very different ideas. Our gun rights are certainly in danger, but what is the source?
Politicians such as Nancy Pelosi, Chuck Schumer, Drane Feinstein, et al. Where do these get their power from? They were elected -- which brings me to another source of danger to our gun rights.
Our own fellow countrymen, who are either ignorant, ill-educated, or have a deliberate thought out agenda intending to disarm us.
I think we shouldn't conflate these issues. Keep your eye on the target, identify the problem, and keep your eyes clean so as not to be distracted by conflationary pettifoggery.
That's my two cents ...