A superstar singer, a sea of flags,

and some meme-worthy mittens.

I, Joseph Robinette Biden Jr, do solemnly swear...

This is how America

officially welcomed its new president, Joe Biden...

So help me God. MAN: Congratulations, Mr President.

Thank you. (CHEERING)

..and its first female vice-president,

Kamala Harris.

I, Kamala Devi Harris, do solemnly swear...

But after a big day for waving,

more waving and some serious fireworks,

it was pretty much straight down to business.

The president has promised to tackle some teeny-tiny problems,

like fixing the economy,

ending racism, fighting climate change,

oh, and dealing with the world's biggest outbreak of COVID-19.

Actually, they're pretty big!

400,000 Americans have died.

That's more than have died in all of World War II.

But on top of all of that

is the tough job of trying to unite a divided country.

Over the holidays,

you might have seen some pretty dramatic pictures

from the US Capitol.

(SHOUTING)

These were supporters of Donald Trump,

who had just spoken to a crowd in Washington.

We fight like hell.

And if you don't fight like hell,

you're not going to have a country anymore.

(CROWD CHANTS)

Since the election, he's been saying that Joe Biden's win was unfair

and that the Democrats cheated.

And while there's no evidence of that,

a lot of his supporters believe him,

and thousands of them stormed the Capitol building

where the federal government sits.

We want our country back!

We are protesting for our freedom right now!

For something like this to happen in a democratic

and mostly peaceful country like the US was a pretty big shock.

Twitter and Facebook even banned

the president's accounts at the time,

saying they were worried

he'd encourage more violence.

And now US politicians have decided to impeach Mr Trump...again.

Donald John Trump engaged in high crimes and misdemeanours

by inciting violence against the government of the United States.

Impeachment is a process written into the US constitution,

which allows the parliament to get rid of a president

who's broken their oath of office.

Donald Trump is only the third

president ever to be impeached.

But, as you might remember, the Senate voted not to remove him.

Now he's become the first president in history to be impeached twice,

and the only one to be impeached after their presidency has ended.

If he's convicted, that'll be another first.

And while he can't be kicked out, because he's already out,

he might be stopped from ever running for president again.

The impeachment trial starts next week,

but back to the new POTUS -

that's President of the United States,

in case you didn't know.

He's already made some big changes, or changed some things back,

including stopping the building of a wall between the US and Mexico,

adding America back onto the Paris climate agreement

to fight global warming,

and making friends with the World Health Organization again.

He's also made wearing masks and social distancing

compulsory across the country,

and says more Americans will be given free COVID-19 vaccinations.

Whether or not it'll be enough to fix the many problems

facing the world's most powerful country,

well, we'll have to wait and see.