The $300 limit is useless. You’ll find, at best, used versions of good brands, or new crap.
The artificial restriction to US manufacturers is also … stupid. And hard to enforce. A number of european firms license US subsidiaries, or have local plants.
Having said that:
“Weird” rounds can be good. The .40SW was once a “weird” round, now it’s the market leader for LEO. Browning/FN have some good choices:
The Hi Power (usually in 9mm)
The FN Five-Seven, in 5.7mm
Another good “weird” round is the .357Sig, which is gaining acceptance.
A good, high-power “weird” round is the 10mm, which is supported by Glock.
The M1911-style pistols are good:
Colt
Smith and Wesson
Kimber
Springfield Arms
and the like all produce fine versions.
Modern alternatives to M1911 include the Sig Sauer P220 and the Heckler and Koch USP series. Glock also supports both .45ACP and another “weird” round, the .45GAP.
The Glocks are excellent low-maintenance, high-abuse weapons, The Glock G22 in .40SW is now the standard issue sidearm for the FBI, as well as a common choice for the standard sidearm for many other LEOs. It is safe and effective, but requires training. Just keep your freaking finger off the trigger: that’s what the trigger guard is for.
Beretta has a nice series of pistols, but they’re better suited for larger hands (M-92/m-9), and there are .40SW variants (M-96), as well as smaller pistols.
If you can’t or won’t pop the money for a Beretta, Taurus has cheaper versions of many of the Beretta designs, at least the 1892-designs.
Sig-Sauer produces expensive but excellent pistols … the P-226 (9mm) and the P-220 (.45ACP) spring immediately to mind.
Smith and Wesson have some of the US LEO market with their semi-autos, usually in 9mm.