It’s a lot of fun to travel around the United States.

There are lots of interesting things to see.

The word of is often reduced.

We write:  a lot of
We say:  /ə-ˈla-də/

We write:  lots of
We say:   /ˈla-tsə/

a lot of skyscrapers
lots of skyscrapers

a lot of tourists
lots of tourists

a lot of historic monuments
lots of historic monuments

a lot of football
lots of football

a lot of football fans
lots of football fans

 

a lot of farms
lots of farms

a lot of animals
lots of animals

a lot of cowboys
lots of cowboys

a lot of beautiful scenery
lots of beautiful scenery

 

a lot of roads and highways
lots of roads and highways

When the preposition of is not reduced…  

we say:  /ə-ˈla-dəv/
we say:   /ˈla-tsəv/

Note:

We write:  a lot of
We can write:  a lotta

We write:  lots of
We can write:  lotsa

Written reduced forms … lotta … lotsa … reflect natural spoken language.
They are only for personal writing, such as emails to family or friends.

They are not standard written English.