What were some of the challenges in the U.S that ex-slaves faced after they were freed?

The American nation did not make provision to integrate
the freed blacks into society.  They were treated in the north and west, and by the
nonslaveholders of the South, as a pariah.

Many or most of
the northern and western states had laws forbidding free blacks from entering.  These
states also had laws limiting the political and economic rights and opportunities of the
free blacks that already lived there.  Pretty soon, the South started copying those
laws.  Upon being freed, the only friend the blacks had was their former owners.  After
the Republican party used the blacks to put itself in power in the southern states, even
their former owners no longer thought well of them.

Under
slavery, blacks had food clothing and shelter from cradle to grave, in sickness and in
health.  Under freedom, they had these needs only so long as they could work, and very
many of them had not had any training or education under slavery that would help them
cope with freedom; furthermore, they were subject to laws that limited their movement
and what jobs they could hold and so on.  It was one generation before the southern
whites recovered the average economic well-being that they had know before the War
Between the States.  It was three generations before the southern blacks recovered the
average economic well-being that they had known before the
war.

The nation did not help them to homestead lands in the
west, because western whites did not want them there.  The nation did not break up
plantations in the South to provide them land.  (That would have been unjust to the
owners, but the reason was that the nation wanted cotton produced on those plantations,
and small farms would not have been very good for
this.)

Two references:

Donald,
Henderson H. 1952. The Negro Freedman: Life Conditions of the American Negro
in the Early Years after Emancipation. New York: Henry Schuman. I found this
book in a university library near-by to my home. Your school librarian might be able to
borrow it for you via Interlibrary Loan, or you may visit a nearby university library
yourself. If it is a state university, it will probably let you check the book out
yourself.

Livingston, Donald W. 2010. "Why the War Was Not
about Slavery," Confederate Veteran, 68, 5 (September/October),
16-22 & 54-60. If you can't find a copy of this article, send me a message, and
I can send it to you.