Of the last 10 Presidential terms spanning 40 years, Republicans have held the office for 5 and Democrats for 5. Each party has likewise held around half the seats in the House and Senate. This has nothing to do with the voters, it's the structural outcome of a FPTP voting system. You get two parties and they each get around half the votes/seats.

The US federal government has also played a major role in causing this by passing laws like DMCA 1201 and the CFAA which incumbents use to threaten competitors who attempt adversarial interoperability.

Moreover, the DoJ budget is ~$33B whereas e.g. the military budget is ~$1T, so arguing that the only way to allocate more resources to antitrust enforcement or similar is to raise taxes would imply that all of the existing spending is critically necessary and Congress never e.g. buys tanks the Army doesn't want or otherwise poorly allocates existing funds.

The US Government spends a preposterous amount of money, and the number only ever goes up. It doesn't need to be bigger, it needs to be less inefficient.