To estimate this, we need to consider the number of internet users in the U.S., the percentage of these users who use Google, and how many searches they make per day on average.

The U.S. has a population of around 330 million and internet penetration is quite high, around 90%, which gives us approximately 297 million internet users.

Google dominates the search engine market, let's assume around 90% of internet users use Google. This gives us around 267 million Google users.

Consider how frequently someone might use Google in a day. Some people might use it only once or twice a day, while others might use it dozens of times. A reasonable average might be 5 searches per day.

So, multiply the number of Google users by the average number of searches per user: 267 million users * 5 searches/user = approximately 1.335 billion searches per day.

Therefore, the estimated daily volume of Google searches made in the United States is around 1.335 billion.