Question

Which claim is the most effective for an argument that technology and the Internet have brought young people closer together?

Technology and the Internet are bringing people, including teenagers, closer together every day.
There are many reasons technology and the Internet have generally brought teenagers together, but there are also many reasons it causes divisions between young people.
Technology and the Internet allow people to share experiences, news, and information almost instantly, bringing young people closer together than ever before.

Answer 1

Option 3 is the most effective.

Why: it gives a clear causal mechanism (“allow people to share experiences, news, and information almost instantly”) and makes a specific, debatable claim (“bringing young people closer together than ever before”), which is exactly what you want for an argument.
Why the others are weaker: #1 is vague and absolute (“every day”) with no mechanism; #2 undercuts the thesis by immediately conceding the opposite.

Suggested tightening: "By enabling the instant sharing of experiences, news, and information, technology and the Internet have brought young people closer together than ever before."

Tip: follow this claim with concrete evidence (social media, gaming communities, shared cultural trends, cross-border collaboration, messaging apps) and address likely counterarguments briefly.