What are the main obstacles to becoming IFR-rated in USA?
The problem is an instrument rating is expensive, time consuming and requires much more - expensive - proficiency related activity. If you are only flying 20-50 hours a year like most PPLs, it's pretty hard to come up with a "business case" to spend the 10-15 grand for getting one if you're not doing serious travel regularly, just from the standpoint of return on investment, let alone staying proficient.  

In other words, the majority of PPLs simply don't fly enough to justify an IR.  The majority that do usually have their own a/c and use it a lot on business, or it's a stepping stone on a career progression.  And even if you have an IR, if your airplane doesn't have airborne weather radar and equipment for flying in icing, you are still pretty limited in your travel at certain times of the year (generally, to under the freezing level and far away from convective weather unless you like taking chances).

If you study a lot of VFR/IMC accidents you find that it's mostly people doing VFR travel for extended distances and time frames.  A light aircraft being used for travel in VFR weather is a very unreliable travel method and pilots have to accept that; too many don't. 

So the big problem is people don't allow for weather delays in schedules, so they push weather to get home.  If you travel places VFR for time frames beyond the next day or two (about the limit you can depend on forecasts most of the time) you have to treat it like flying standby on the airlines; always ready to wait a day or two to get where you're going.  When you build this into your planning (like planning to be home 3 days before you have to return to work instead of the day before) you can relax a bit, and the risks of getting caught in a get-home-itis trap go down dramatically.