My humble suggestions (subject to all possible disclaimers*):
1 ) Check out the "Show us yer Stuff" thread.
You can spend a great deal of time enjoying the many many pages of that thread, and you will see many wonderful pictures of superbly painted GHQ minis. Note in particular JB's posts on infantry -- they include a fair number of US Vietnam era and moderns. Note also Ritter's posts on infantry -- not so much focussed on moderns, but truly inspiring to those who want to paint GHQ micro infantry forces.
2 ) Disregard all suggestions of going to 10mm or 15mm!
No, those posted suggestions are not "wrong". There is much fun to be had at those scales, I'm sure. But ... if you want to get going with 1/285th (6mm) infantry, don't be put off! You can have some wonderful wargaming experiences with this scale, even doing primarily infantry combat! If you really do want to focus on infantry, look for rules that are "fire-team" or "half-squad" based. These usually focus on 2- and 4-man teams, making a squad (of 8-12 men) by combining one or two fire-teams of 4 men with a 2-man support team or two. They provide generally provide for very interesting tactical action, in many ways better than the 1-to-1 skirmish rules used with some of the larger scales.
3 ) Don't start out by thinking of kit-bashing Isreali's into US.
It is indeed possible, and quite enjoyable, to kit-bash the GHQ stuff around. But it is probably not a good place to start. This scale is really small. You will be better advised to develop the skills of painting and mounting up the units as they are first, so that you can also get going with gaming. Then you can start kit-bashing and customizing stuff to your personal tastes.
Photos of some of my experiences with micro-scale infantry, to wet the appetite:

My WW2 Italian infantry, completed a few months ago. These are GHQ figures.

WW2 Italian AT and AA guns to support my infantry. Again, GHQ figures.

My WW2 Soviet light armor overruns a German OP during a wargame with a friend. All GHQ in this pic.

WW2 German sappers blow a bridge as mortar rounds fall about their ears during a Kursk scenario I put on at a gaming con more than a year ago. Paloalto (of this forum) won a GHQ gift certificate for this particular action by his troops. Figures are GHQ.

Modern US and Iraqi infantry fight it out for a bridge in a scenario I played taken right out of a US War College study. This is probably the most topical. Vehicles and figures are GHQ. Infantry are modern Soviet and modern US GHQ figures.
How's that? Enough to get your engine started?
-Mark 1
*Note: This is an invited editorial, and does not necessarily reflect the views of management.
Your mileage may vary. These are skilled professionals, do not try this at home (well, actually, DO try this at home). Published results not typical. No animals were harmed in the typing of this post. blah mumble blah ...