如果中国成为世界第一大经济体，会带来怎样的影响？

翻一下历史。
美国成为第一是在1895年左右，1899年大英帝国开打布尔战争，损失了相当于六次甲午中日战争的赔款，一下子就不行了，美国一直维持着中立政策，在1917年终于开始参加一战，并且在战后由威尔逊总统筹集建立国联，不过后来美国没参加。
根据美国的前车之鉴，猜想的话，中国在GDP超过美国后较长时间内依然会保持国际中立政策，不会较大程度的军事干预，当然由于中国人口较多，按照人口比例可能比当年英美更大，不排除中国可能会有加速情况，差不多在20年内会有第一次真正的政治军事倾斜，会有真正的政治军事同盟，到时候是谁还不好说。
在第一次政治军事同盟之前，整体中国是非常安全的，预计会改善和所有国家的关系。
中国会被动输出一些意识形态方面的东西，可能都不是中国故意要输出的，实际上现在已经有苗头了，《纽约时报》有关于这方面的论述，可能对西方影响不是很大，顶多可能让西方人了解一下中国，但是对发展中国家影响比较大，尤其是非洲，拉美以及东南亚。
比较激烈的时段是在2012年和2013年时间，西方媒体长篇大论论述中国模式的缺点，那会也正值中非关系紧密期间，不少国家领导人公开宣称要用中国模式
冷战结束20年来，自由市场和多党制的民主被视为理想的治理形式（它也是获得华盛顿支持的一个关键）。然而现在，由于受到了快速增长的亚洲经济体，如中国、新加坡、马来西亚的先例所吸引，而这些国家都在推动现代化的威权政府治下取得了可观的经济增长，一群非洲领导人开始公开宣扬，他们羡慕那种形式的政府。
《纽约时报》2013年12月17日
实际上中国模式没什么特殊的，也不神秘，只不过西方国家自己把事情搞砸了，像菲律宾之类的，在意识形态，国家制度甚至连同宗教方面都百分之百追随美国的国家，搞的不太好。我觉得同理心这个东西是很重要的，在西方国家认为比较重要的多元化，自由的价值观之类的，在发展中国家不是那么重要，而发展中国家最迫切需求的其实就是钱。这话说的有点俗，但是其实就是这么回事。
像美国已经着手关于意识形态方面的法案，在参议院已经开始审议类似的东西，例如说
Countering Information Warfare Act of 2016
贴几条给你们看看
It is the sense of Congress that—

(1) foreign governments, including the Governments of the Russian Federation and the People’s Republic of China, use disinformation and other propaganda tools to undermine the national security objectives of the United States and key allies and partners;
(2) the Russian Federation, in particular, has conducted sophisticated and large-scale dis­in­for­ma­tion campaigns that have sought to have a destabilizing effect on United States allies and interests;
(3) in the last decade disinformation has increasingly become a key feature of the Government of the Russian Federation’s pursuit of political, economic, and military objectives in Ukraine, Moldova, Georgia, the Balkans, and throughout Central and Eastern Europe;
(4) the challenge of countering disinformation extends beyond effective strategic communications and public diplomacy, requiring a whole-of-government approach leveraging all elements of national power;
(5) the United States Government should develop a comprehensive strategy to counter foreign disinformation and propaganda and assert leadership in developing a fact-based strategic narrative; and
(6) an important element of this strategy should be to protect and promote a free, healthy, and independent press in countries vulnerable to foreign disinformation.

扒拉扒拉还有很长

其中这个比较有意思

Information Access Fund.—
(1) AUTHORIZATION OF APPROPRIATIONS.—There is authorized to be appropriated to the Secretary of State for fiscal years 2017 and 2018 $20,000,000 to support the Center and provide grants or contracts of financial support to civil society groups, journalists, nongovernmental organizations, federally funded research and development centers, private companies, or academic institutions for the following purposes:
(A) To support local independent media who are best placed to refute foreign dis­in­for­ma­tion and manipulation in their own communities.
(B) To collect and store examples in print, online, and social media, disinformation, misinformation, and propaganda directed at the United States and its allies and partners.
(C) To analyze tactics, techniques, and procedures of foreign government information warfare with respect to disinformation, misinformation, and propaganda.
(D) To support efforts by the Center to counter efforts by foreign governments to use disinformation, misinformation, and pro­pa­gan­da to influence the policies and social and political stability of the United States and United States allies and partners.
(2) FUNDING AVAILABILITY AND LIMITATIONS.—All organizations that apply to receive funds under this subsection must undergo a vetting process in accordance with the relevant existing regulations to ensure their bona fides, capability, and experience, and their compatibility with United States interests and objectives.

如果这个法案通过了，那基本上传说中的“美分党”就正式露出水面了。
感觉这个法案和这次民主党被俄罗斯黑客糊了一脸屎有关。

另外千万别说我造谣
Text - S.2692

美国国会官方网站的，英文好的可以自行翻译一下。

呵呵，看我的答案每天可以给你不同的姿势。