Is it virtually impossible to avoid HFCS when buying food over there?
You can avoid HFCS by purchasing whole foods such as fruits, nuts and vegetables (source 1, source 2, source 3, source 4), so it's a matter of choice.
Is there high fructose corn syrup in almost every grocery product in America?
This depends on whether you are talking about packaged foods only. You can see from the sources above that there are alternatives, however the USDA had this to say in 2000:
Sugar— including sucrose, corn sweeteners, honey, maple syrup, and
molasses—is ubiquitous and often hidden. In a sense, sugar is the
number one food additive. It turns up in some unlikely places, such as
pizza, bread, hot dogs, boxed mixed rice, soup, crackers, spaghetti
sauce, lunch meat, canned vegetables, fruit drinks, flavored yogurt,
ketchup, salad dressing, mayonnaise, and some peanut butter.
Carbonated sodas provided more than a fifth (22 percent) of the
refined and added sugars in the 2000 American food supply, compared
with 16 percent in 1970.
The USDA also previously had a database which showed some typical analysis for foods to identify added sugars. On a page marked last updated 2012 it now says this regarding the previous mentioned database:
No method can analyze for added sugars so their amounts must be
extrapolated or supplied by food companies, many of which are not
willing to make public such proprietary information.
This document around labeling requirements for sugar is also worth reading as it also goes into great detail around the lack of solid requirements to label sugars on packaging in the US.
Based on this information I would say if you are not going with whole foods then it is going to be difficult to tell. Your best option is to stick with fresh produce, nuts and meats. Anything packaged and you are heading into an area which is uncertain.