The increased wear & tear on the nation's highways due to today's heavier trucks, can be attributed to several factors, including increases in maximum gross vehicle weights, and the age of the highways themselves.
The interstate highway system was designed in the early 1950's, when normal truck gross weights were in the 68,000 lb to 72,000 lb range. Due to pressure from the trucking industry, and safer tires & brakes, the various state & Federal regulators allowed M - GVW's to be increased all through the 1970's & 1980's to today's minimum nationwide GVW of 80,000 lbs. This can be increased , depending on the state, up to Michigan's 145,000 M - GVW !!! Of course the more weight the truck hauls, the more rubber you have to have on the road; just keep adding axles.
Ironically these increases in allowable GVW came as the Interstate highway system was nearing completion; built to the lesser standards of the 1950's. Some of the oldest segments of the Interstate highway system have reached the end of their design life, & need to be rebuilt. Interstate 5 in Oregon's Willamette & Rogue River Valleys is undergoing a multi - year project to rebuild virtually all its' bridges.
Yes I agree that the nation's trucking industry is subsidized to a degree, just as the barges & airlines are also. None of them pay the full cost of their right of way the way railroads do. Welcome to the Wonderful World of U.S. railroading.